有轨电车的做法图纸

depending where you're from this is a tram， a trolley or a streetcar whatever， you call it the urban railway is making a comeback at one time almost all city transit ran on rails， but then buses and cars took over new technology no emissions and ease of installation has given this form of mass transit a new lease on life trams run on electricity and the latest versions can actually generate some of their own power let's see how they work choosing low emission trains over gas and diesel power is great for pr and government pocketbooks， but for this ride to appeal to the masses you need more than that to be number one in the public eye， you have to be efficient reliable and comfortable let's start with efficiency compared to other forms of mass transit like buses trams need a lot less， energy and maintenance their electric motors are more powerful quieter and efficient than their gas guzzling cousins trams get power from overhead lines fed by the local grid through something called a pantograph it draws electrical current through points of contact early versions of this device had a problem constant rubbing from overhead wires wore out contacts and cut off power now overhead lines are laid out in a zigzag pattern so the pantograph slides side to side while the tram is in motion greatly extending the life of its contacts electricity flows from the wires to copper coils inside the motors this creates a magnetic field that spins a magnet and with it the wheels this machine can top one hundred kilometers an hour， but rarely goes above seventy while working in cities and that means it needs good breaks， but these ones aren't just for stopping they also help feed electricity back into the system a design feature that can save big on a city's power bills when the machine needs to stop the power is cut off to the motors， but the tram's momentum keeps the wheel spinning and this allows the motors to generate power it's called regenerative braking the momentum spinning inside the motor creates an electric current that sent back up through the machine through its pentagraph along the overhead wire and into the nearest tram an electrical piggy back ride and if the tram needs to stop in a hurry， it's also got sets of air brakes in an emergency say if something falls in front of the tram the brakes all work together with a safety bar to prevent anything from getting stuck under the machine step two in winning over the public is reliability and that means not breaking down with no transmission no potholes to deal with no tires to go flatten no fuel to run out of the only thing that really threatens this ride is a power failure trans like these do cost a lot more to purchase than buses， but they last decades longer and cost much less to run on a day to day basis coming across as good for the environment and city bank accounts is fine， but it doesn't explain why the average person prefers light rail to buses for that you need to look at this machine's third advantage comfort and style new models come with street level ground clearance for easy on and off they can grow with extra cars to give plenty of rush hour， elbow room and with steel wheels that can be kept true the ride is super smooth the low ride comes courtesy of a design that hides most of the trams components on the roof giving the wheels and axles plenty of room to provide support super strong pivot points seamlessly join the cars together and enable these machines to take on up to seven cars and still slide through corners accordion like rubberized material fills in the gaps around the joints between the cars it's rush out and now you have transit that's easy to board with continuous open space for over two hundred passengers keeping a ride smooth has always been a challenge for machines that depend on steel wheels riding steel rails and the wheels wear out fast especially under a tram that has an empty weight of over forty tons so every twenty thousand kilometers they get a tune up a diamond tip truing machine this big robot shaves off half a millimeter thick strips until the wheel is perfectly clean and level it guarantees a smooth ride and reduces friction saving big on electricity fast smooth and cheap to run with cities increasingly building more right of ways for the tram， the other options are looking a little older every day。